set [\x.x : Bool -> Bool, \x. not x]
{\x.x : Bool -> Bool, \x. not x}
{\x.x, \x. not x} : Set (Bool -> Bool)
{\x.x, \x. not x}
bag [\x.x : Bool -> Bool, \x. not x]
[\x.x : Bool -> Bool, \x. not x]
{} : Set (Bool -> Bool)